Swap on short sale?

I am just wondering exactly what the swap field is in MT4. I would assume it has something to do with interest differentials of the short position??? Any help would be great.

Swap is a debit or credit as reflection of differences of interest rates in respective currency pair countries.
Example:
If you are long GBP/USD and US interest rates are lower than GBP interest rates you will earn a credit.
If you are short the pair, you would be debited.
Hope this helps,

Cheers for that I thought it would something along those lines.